Apparatus for the production of hydraulic cement



Aug- 3, 1965 R. G.'ScHLAUcH 3,198,247

APPARATUS FOR THE PRODUCTION OF HYDRAULIC CEMENT Original Filed Aug. 5,1958 INVENOR. RICHARD e. SCHLAUCH BY im@ iM m United States Patent O3,198,247 APPARATUS FUR THE PRGDUCTEN F HYDRAULIC CEMENT Richard G.Schlauch, Allentown, Pa., assignor to Fuller Company, Catasauqua, Pa., acorporation of Delaware Original application Aug. 5, 1958, Ser. No.753,227, now Patent No. 3,043,703, dated .Iuiy 10, 1962. Divided andthis application Oct. 19, 1961, Ser. No. 146,243

2 Claims. (Cl. 165-94) This is a division of application Serial No.753,227, tiled August 5, 1958, now Patent No, 3,043,703 granted July 10,1962.

The present invention relates to apparatus for the extraction ofvolatilized matter from gas streams and is more particularly concernedwith the selective extraction of compounds of the alkali metals andother volatilized matter in the form of vapors, fumes or otherdispersions of solid or liquid matter from the gases issuing from cementproduction zones in general, and especially from reaction zonesproducing hydraulic cements typified by Portland cement.

While the invention is discussed herein with particular reference tovolatilized alkalies, it is to be understood that similar selectiveextraction of excesses of other volatilized matter, such as sulphatecompounds, is contemplated.

In many hydraulie cements, compounds of the alkali metals, hereinafterreferred to as alkalies, are found which lare derived from similar orother alkali compounds originally present in the raw materials. Whenthese alkalies are present in hydraulic cement clinkers of the Portlandcement type, in excess of about 0.6%, expressed as their molecularequivalent of sodium oxide, the excess is detrimental to the ultimateutility of concrete produced from such cement. In some cases, as in massconcrete structures and in highway construction, especially whensiliceous aggregates are t0 be used, the presence of such quantities ofalkali make the cement unacceptable to the authorities responsible forthe construction.

Substantial percentages of the amount of alkali present in the cementraw materials `are generally driven off the raw materials during itsexposure to the cement-forming reaction temperatures in excess of 2000F. The alkalies thus driven off are then carried in the gases dischargedfrom the cement-forming reaction zone. It is believed that the alkaliesthus driven off occur in several compound forms. When cooled, thesealkali compounds tend to sublime or to condense to an ultimate solidphase at and below their condensation points.

Since the gases discharged from such reaction zones generally also carrya substantial portion of material particles, at least a portion of suchparticles preferably are removed from the gases and returned to thereaction zone to avoid waste of material, as well as avoiding dustnuisances. However, the gas temperatures encountered are normallyconsiderably above the maximum temperature limitations of contemporarydust collecting equipment.

In order to reduce the gas temperatures to the required value, usuallybelow 600 F., previous expedients have employed the tempering of the gasby introduction of atmospheric air, or the cooling thereof by liquid orwater sprays and dispersions. However, this temperature reductioninduces deposition of the alkalies on the surfaces of the materialparticles, and the return thereof to the reaction zone with theparticles, thereby increasing the percentage of alkali in the materialdelivered to the reaction zone.

Furthermore, there is an increasing trend to utilize the heat content ofgases discharged from such reaction zones for preheating raw materialsprior to their introduction PCC to the reaction zone. When thepreheating is effected by direct contact of the gases with the rawmaterial, the alkalies present in the gases are prone to condense andadhere to the raw material particles and to return therewith to thecement-forming reaction zone. Therefore, an artificially high alkalicontent is established in the incoming raw material and since only aportion or a percentage of alkalies introduced with the raw material isdriven therefrom in the reaction zone, an undesirable percentage isoften passed through the reaction zone and is present in the finalcement product. No entirely satisfactory solution to this problem hasbeen known.

In accordance with the present invention, the hot gases passing from thereaction zone Where cement is being produced and which contain volatileconstituents driven off the cement-forming material during thecement-forming reaction are caused to impinge upon a condensing surfaceto bring about condensation of the entrained volatile components uponsaid surface, from which they periodically may be removed. In oneembodiment of the invention, the exposed surface of the condensedcomponent is maintained at a temperature at which it is in a tacky phaseto facilitate adherence thereto of solid matter entrained in the gases.

In general, a preferred form of apparatus of the present invention, asemployed in conjunction with the production of hydraulic cements of thePortland cement type, comprises one or more condensing surfaces ormembers maintained at a temperature below that of a vapor component ofthe gases, which may comprise a plurality of tubes cooled by a fluid orliquid such as water, and which are arranged across the interior of asection of conduit adjacent to and leading from a cement-producingreaction zone. The cooled tubes promote condensation of vapors andadherence of liquid and solid particles on their surraces.

Means are provided for removing, either continuously or at intervals,the material accumulated on the tubes for discharge from the process.This may comprise means for reciprocating the cooled members throughcleaners or Scrapers positioned adjacent the conduit, and when required,may include a hopper having a valved discharge located beneath thecleaners to collect the removed material for separate discharge. theinvention may be derived from the accompanying drawings and description,in which:

FIG. l is a vertical sectional view of a form of apparatus of theinvention; and

FIG. 2 is a sectional view taken along the lines 2--2 of FIG. l.

As shown in FIGS. 1 and 2, one .preferred form of apparatus, for use inthe production of Portland cement, comprises a casing or conduit 1leading from a kiln or reaction zone discharging volatilized alkaliesand gases. The conduit 1 comprises a plurality of walls 2, 3, 4 and 5,respectively, which are internally lined with a suitable insulation 6.

The walls 3 and 5 are providedwith apertures 7 and 8, respectively,which communicate with lateral branches 9 and 10, respectively. Thelateral branches 9 and 10 are, in turn, provided with apertures 11 and12, respectively, which are aligned with apertures 7 and S transverselyof the conduit 1. The lateral branches 9 and 10 are provided in theirlower regions with discharge apertures 13 and 14, respectively, whichcommunicate with discharge hoppers 15 and 16, respectively. The hoppers15 and 16 are provided with valves 17 and 18, respectively, when airlocks are required to prevent substantial leakage into or out oftheconduit.

The apertures 11 and 12 are closed by a plurality of Scrapers 19,secured therein by bolts 20 engaging the A better understanding of iWalls of the extensions, preferably with a limited amount of free playin the exact position of the scrapers. Each of the scrapers 19 isprovided with a bore 2l extending therethrough in a direction preferablysubstantially transverse to the axis of the conduit 1L. The bores of therespective Scrapers of lateral extensions 9 and I@ are aligned in pairsto receive a plurality of tubes 22 therethrough, which extendtransversely across the conduit 1 in the path of the gas owtherethrough. The tubes 22 may be formed of stainless steel or anymaterial of construction appropriate to the temperatures to beencountered. As shown, the tubes 22 are arranged in vertical pairs witha plurality of such pairs spaced across the conduit 1. However, it iscontemplated that any suitable arrangement of tubes or equivalent solidmembers, which will result in an intimate contact of the gases with suchtubes, may be employed. It is also contemplated that instead of thetransverse tubes shown, other solid members which are suitable forintroduction to the interior of the conduit 1 may be employed,preferably in a manner assuring the presence of an adequate number ofsolid members or area of collecting surface in a conduit at any giventime.

The ends of each of the vertically spaced pairs of tubes 22 areconnected by fittings 23 and 23 to flexible hoses 24 and 24respectively. A regulated supply of cooling fluid, such as air or water,is delivered from a source (not shown) to one of the hoses 24, 24 ofeach vertical pair of tubes. It is immaterial to the invention in whichdirection, with respect to FIGS. l and 2, the liquid is passed throughthe tubes.

Means are provided for reciprocating the tube assemblies in alignmentwith the bores of the Scrapers 19. This may take the form of anhydraulic ram, not shown, having a connecting rod 25 connected to one ofthe fittings, such as the fitting 23, or any other suitable mechanicalmeans for reciprocation. Alternatively, the tubes or equivalent solidmembers may be static and the cleaning elements moved in relationthereto, in which case the masses of matter removed from the tubes maybe collected in a lower portion of the conduit and subsequentlydischarge therefrom.

The Scrapers 19 are provided with inner scraping edges 26 which engagethe external periphery of each of the tubes 22, and are adapted toscrape accumulated material from the surface of the tubes as the tubesare passed therethrough. The limited free play of the Scrapers willaccommodate slight variations in alignment or uniformity of the tubes.Material thus scraped from the tube surfaces is then free to falldownward into the hoppers 1S and 16, whichever may be the case, and isthen discharged therefrom by the valves 17 or 18.

In operation, the gases from the cement-producing reaction zone arepassed through the conduit l. The cooling uid, either air, or preferablywater, is then passed through the appropriate hose 24, 24', fitting 23and associated tubes Z2 to cool the tubes and is thereafter dischargedthrough the opposite hose 24, 2li. The maintenance of the tubes 22 at atemperature below that of the gases and particularly below thecondensation point of a substantial component of the volatilizedalkalies present in the gas causes a condensation and adherence thereofon the tube surfaces. The condensate preferably is sublimated anddeposits on the tube surfaces in a substantially solid ultimate form.However, the presence of the condensing matter on the tube surfaces willpromote the adherence of further dispersione of solid or liquidparticles, when a partially or generally tacky surface of the condensateoccurs either momentarily, as a transition state of the condensate, orpermanently as the ultimate form of the condensate at that temperature.The greater portion of the deposited matter is accumulated on theupstream surface of the tubes. The term sublimation is used herein asdefining a condensation of volatilized matter to a sold phase withoutsubstantial or apparent transition through a flowing liquidv phase.

Either continuously, or at intervals which are best determinedexperimentally as discussed more fully hereinafter, the tubes arereciprocated from one extreme lateral position to the opposite extreme.As shown in FIG. l, the tubes are in the extreme left hand position.Upon motion of the tubes towards the right, as viewed in FIG. l, thecutting edges 26 of the Scrapers 19 of lateral extension 9 scrape theaccumulated matter from the surface of the tubes, whereupon it fallsinto the hopper 15 for discharge to the valve 17. Subsequently, thetubes are moved to the left, as viewed in FIG. l, and the scrapers 19 oflateral extension l0 clean the newly accumulated matter from the tubesfor discharge by the hopper 16 and valve t8.

The removal of the accumulated matter from the condensing surface willgenerally be facilitated by shrinkage or contraction of the tubes andthe accumulated mass, at dissimilar rates, under the inlluence of thecooling medium and upon removal from intimate contact with the extremetemperatures of the flowing gases. In some instances, the deposit ofmaterial generally will tend to crack and separate from the condensingsurfaces as soon as they are both removed from the main ow of the gases,thereby minimizing the cleaning or scraping force required.

Variables such as the velocity and temperature of the gas, the amount ofvapors or material to be extracted from [the gas, and the number ofsolid members or the 'total effective condensing surface area of thesolid members, all generally affect the rate of deposition of condensateand adhering material. Therefore, the duration of retention of a givenarea of the condensing surfaces in the gas stream, which is a functionof either the interval between shifts of the apparatus of FIG. l or therate of linear motion of the tubes =when in continuous reciprocation,-is best determined experimentally. Furthermore, it is preferable toprovide means for regulating the duration of retention of the condensingsurfaces in the gases to accommodate changes in one of these variables,as in likely to occur within limits, in cement-producing reaction zones.

A further factor which may affect the determination of the preferredduration of the condensing surface within the gas stream, as in theexample cited hereinafter, is that of a variation in composition of theaccumulated matter upon continued deposition. A heavy accumulation ofmatter `on the condensing surfaces not only may impair the eiciency ofthe unit but, in some cases, also causes a change in the fraction of thegas-stream content which is extracted. It is believed that this is theresult of a rising condensing-surface temperature caused by theinsulating effect of the accumulated matter, and a consequent reductionin either the amount of volatilized matter condensed thereby, or therate of completion of the condensation process, or both.

For the selective extraction of -alkaflies in the production olfPortland cement in conjunction with a direct gas-contact raw materialpreheater, lit has been found generally preferable to ylimit theaccumulation of material on any condensing surface to a maximum depth orthickness of about one-sixteenth of an inch. For example, in aninstallation producing Portland `cement and including a rotary cementkiln lassociated `with a preheater of the type shown in the patent toMuller et al., U.S. 2,663,5607 issued December 22, 1953, two inch blacksteel pipe was inserted transversely yinto the gas stream passing fromthe kiln to the preheater, and the water supply therethrough IwasIregu-lated to produce a to F. temperature `in the -water after passagethrough the gas-contact portion of the pipe. The `gases leaving the kilnwere .in the order of l9002000 F. The gases were then passed in directheat exchange relation with the feed for the kiln to preheat the feedmaterial, and

sucses? then through dust separators. The separated dust was returned tothe reaction zone, all in the manner disclosed in the aforesaid patent.

After approximate-ly one minute of exposure to the gases, a coating of`white solids was accumulated to a depth of about 64. Analysis of thisdeposit disclosed the presence of 29.65% potassium oxide and 1.17%sodium oxide, by weight.

Continued deposition beyond the first minute, up to and including a tenminute overall exposure time, yielded a yellowish brown material depositover the whitish deposit, which, upon analysis, was found to containonly 16.56% potassium oxide and 0.8l'% sodium oxide, by Weight, andcontained substantially greater amounts of dust of cement-formingcompounds.

The higher percentage of alkali in the layer `of material next to thettubes is due to the fact that the tubes were sutliciently cold that thevolatilized alkali in the gases condensed thereon in a solid state`which impeded the yadhesion .thereto of dust particles in the gases. Asthe deposition of material on the tubes increased, it had an insulatingeffect with the result that (the exposed sur- Iface of the depositedmaterial was at a lower temperature and in a tacky phase. When theexposed surface reached that stage, dust particles adhered thereto to agreater extent, with resultant increase in the percentage of dust in thedeposited material `and a corresponding decrease in the percentage ofthe alkali therein.

While this change in the percentage ycomposition of matter accumulatedunder prolonged exposure may not occur in all processes to which thepresent invention may be applied, it is likely to be encountered and t-obe of particular interest when Ithe invention is used yfor the selectiveextraction of volatilized matter in the production of hydraulic cementin conjunction with a directcontact, raw material preheater. =ln .thesecases, it is generally desirable to retain the cement product or raw:material dusts in the system for return to the reaction zone with theincoming preheated raw material. Therefore, it is Kadvantageous to havesuch dust continue in the gases to the preheating stage where it isbrought into contact with and joins the raw material, rather than beingextracted in large percentages with the condensed alkalies.

In some cases, the rise in temperature of the condensing surface, `whichsurface becomes that of :the accumulated -fmatter after continueddeposition, may take that `surface above the condensation point of avolatilized component of the gases, thereby substantially .precludingfurther extraction of that component. Also, the reduced heat transferrate from a newl -deposited condensing particle through the accumulatedsolid matter to the cooled surface of the tube or solid member mayestablish or prolong an intermediate, liquid or tacky phase of thecondensing particle. The prolonged liquid or tacky .phase d is thenprone to cause the adherence of increased or excessive amounts ofmiscellaneous particles encountering the condensing surface.

Where the total collection of matter is of prime importance, rather thana critical control over the generally selec-tive extraction of onecomponent in preference to another, a prolonged liquid or tacky phasemay be established by permitting a substantial build-up of matter on thecondensing surface. Alternatively, regulation of the temperature of the`condensing surface of the solid member itself may be employed to reducethe velocity of the completion of condensation and sublimation, therebypermitting lesser intervals between cleaning of the condensing surfaceor a higher rate of cleaning thereof when prolonged exposure makesremoval of the deposit more difficult.

Various changes may be made in the details of the `invention asdisclosed Without sacrificing the advantages thereof or departing fromthe scope of the appended claims.

lclaifm:

Apparatus for removing matter from a gas stream comprising `a conduitthrough which the 'gas stream is caused to flow, at least one condensingsurface in said conduit in the path of a stream of gases passingtherethnough, means for maintaining in the condensing surface atemperature below the solidiication point of -a vapor component of thegas stream, said conduit having lateral extensions extending therefromthrough which said condensing surface extends, Scrapers positionedwithin the lateral extensions adapted to engage the surface of thecondensing surface, means for reciprocating said condensing surfacerelative to said scrapper for removing the solidified matter deposite-don the condensing surface and discharge hoppers extending downwardly1Afrom said extensions and directly below the Scrapers, whereby materialscraped Vfrom the condensing surface will fall into said dischargehoppers and be discharged from the conduit separately from the gases.

2;. An apparatus for removing matter from a gas stream las set forth inclaim l, in 4which said condensing surface is a tube and which includesmeans for circulating a coolant through said tube.

References Cited by the Examiner UNlTED STATES PATENTS 1,548,158 8/25Murray 155-5 1,844,308 2/32 Annacost 16S- 86 2,364,279 12/44 Dodge62-438 2,761,668 9/56 Sylvest 263--32 2,774,573 12/56 Holm 165--6 CHRLES SUKALO, Primary Examiner.

PERCY L PATRXCK, Examiner.

1. APPARATUS FOR REMOVING MATTER FROM A GAS STREAM COMPRISING A CONDUITTHROUGH WHICH THE GAS STREAM IS CAUSED TO FLOW, AT LEAST ONE CONDENSINGSURFACE IN SAID CONDUIT IN THE PATH OF A STREAM OF GASES PASSINGTHERETHROUGH, MEANS FOR MAINTAINING IN THE CONDENSING SURFACE ATEMPERATURE BELOW THE SOLIDIFICATION POINT OF A VAPOR COMPONENT OF THEGAS STREAM, SAID CONDUIT HAVING LATERAL EXTENSIONS EXTENDING THEREFROMTHROUGH WHICH SAID CONDENSING SURFACE EXTENDS, SCRAPERS POSITIONEDWITHIN THE LATERAL EXTENSIONS ADAPTED TO ENGAGE THE SURFACE OF THECONDENSING SURFACE, MEANS FOR RECIPROCATING SAID CONDENSING SURFACERELATIVE TO SAID SCRAPPER FOR REMOVING THE SOLIDIFIED MATTER DEPOSITEDON THE CONDENSING SURFACE AND DISCHARGE HOPPERS EXTENDING DOWNWARDLY